2 Samuel 5:4 KJV
David was thirty years old when he began to reign, and he reigned forty years.
2 Samuel 5:4, King James Version
In context
3 So all the elders of Israel came to the king to Hebron; and king David made a league with them in Hebron before the Lord: and they anointed David king over Israel.
4 David was thirty years old when he began to reign, and he reigned forty years.
5 In Hebron he reigned over Judah seven years and six months: and in Jerusalem he reigned thirty and three years over all Israel and Judah.